Reflective liquid level sensor based on modes conversion in thin-core fiber incorporating titled fiber Bragg grating

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Biomedical Engineering

Background:

• Accurate liquid level monitoring is crucial in various industrial and scientific applications.
• Traditional sensors face limitations in range, compactness, and environmental immunity.
• Fiber optic sensors offer potential for remote, non-invasive, and robust measurements.

Purpose of the Study:

• To propose and demonstrate a simple, compact, and reflective liquid level sensor.
• To utilize mode conversion in a thin-core fiber with a tilted fiber Bragg grating (TFBG) for liquid level detection.
• To achieve high sensitivity and temperature immunity with an extended measurement range.

Main Methods:

• Fabrication of a thin-core fiber sensor incorporating a single tilted fiber Bragg grating (TFBG).
• Theoretical analysis of mode conversion between core and cladding modes within the TFBG structure.
• Experimental setup to measure changes in collected cladding mode power as an indicator of liquid level.
• Evaluation of sensor sensitivity and temperature cross-sensitivity.

Main Results:

• Successful demonstration of a reflective liquid level sensor based on TFBG-induced mode conversion.
• Observed decrement in cladding mode power correlated with increasing liquid levels.
• Achieved high sensitivity and excellent temperature immunity for the proposed sensor.
• Demonstrated that the sensor's measurement range is not constrained by the physical length of the TFBG.

Conclusions:

• The proposed TFBG-based fiber optic sensor provides a simple and compact solution for reflective liquid level sensing.
• The sensor exhibits high sensitivity and temperature immunity, making it suitable for diverse applications.
• The unique design overcomes the range limitations of conventional TFBG-based sensors, offering a significant advantage.